This proposal is to renew support for a Postdoctoral Research Training Program in Microbial Pathogenesis of Infectious Diseases. Highly successful in its first 20 years, this program has been extensively redesigned to prepare graduates to meet growing workforce needs in translational science. This program has been structured to synergize with an innovative program established for pre-doctoral students at Tufts University with support from the Howard Hughes Medical Institute (MERGE-ID). Both programs utilize a combination of required co- mentorship by a clinical researcher and a basic laboratory scientist as well as coursework and conferences specifically designed to blend a basic science orientation with medically oriented clinical research and to encourage interaction between ID clinicians and basic scientists. This program is designed to train both M.D. fellows in Infectious Diseases as well as Ph.D. fellows interested in studying microbial pathogenesis. Ph.D. trainees take a specially designed course in Medical Problem based Learning that teaches self-learning using cases from the 1st year medical school curriculum. In addition, they participate in outpatient clinics in Infectious diseases to directly observe medical care of specific diseases. M.D. trainees must take graduate level courses in Host-pathogen interactions alongside Ph.D. students in the MERGE-ID program. Although changes have been made to the structure and curriculum, the core of this program remains its outstanding faculty who share an interest in Infectious Diseases. Strengths of the faculty include investigations of: 1) virulence determinants in bacterial, viral, parasitic and fungal pathogens; 2) infections in immunocompromised hosts; 3). Interactions of the host immune system with bacterial, viral and fungal pathogens; 3) interspecies microbial interactions and the impact on infectious disease pathogenesis; 4) clinical study design. The 26 faculty are highly interactive and have a long history of collaboration as evidenced by a large number of shared publications and grants. Another major strength of the program has been the use of Personal Progress Review Committees comprised of 4 faculty members that meet every 6 months to ensure progress of the trainee. This format has allowed the program to achieve a high success rate (>75%) for its trainees in remaining in academic, industrial, or governmental research despite the fact that historically, the majority of the in trainees that have entered the program are M.D. fellows with no prior research experience. The success of the program has translated into continued highly successful recruitment, including among underrepresented minorities that comprised greater than 25% of the trainees during the most recent period. The application requests support for 4post-doctoral trainees per year. Trainees are chosen through a rigorous selection process and are supported for 2-3 years.